Sir Peter O'Sullevan: 'They say that racing is in a state of crisis – well, it has been in crisis for 60 years!'

Brian Viner Interviews: The man known as the 'voice of racing', 90 this week, has seen it all – but is still excited by the prospect of Kauto Star v Denman

Not least of O'Sullevan's many virtues is his refusal to champion the old days over modern times (David Ashdown)

Don't tell my paymasters, but occasionally this interviewing brief throws up assignments that I would do without remuneration; indeed, that I would pay to do. A long, well-lubricated lunch at Le Suquet in Chelsea with Sir Peter O'Sullevan, following coffee in his nearby flat at 11am, and at noon – "are you ready for something a little more interesting?" – a perfectly chilled bottle of rosé, falls squarely into this category. The great man turned 90 earlier this week, yet has lost none of his style, wit and sporadic flashes of mischief as a raconteur, nor any of his celebrated charm, which, if anything, and like the fine wines of which he is such a devotee, gets more impressive with age.

The adjective "great" is bandied about far too liberally in the world of sport, of course, and one is entitled to suspect hyperbole, or judgement addled by memories of Le Suquet's excellent house red, when it is attached to a man who lent merely his voice to half a century of great racing moments. But to describe O'Sullevan as a former commentator, or even more respectfully as the BBC's "voice of racing" for 50 years, does not even begin to cover his contribution to the Sport of Kings.

For decades he has campaigned tirelessly for animal welfare, and since 1997 the Sir Peter O'Sullevan Charitable Trust has put money, oodles of it, where his mouth has always been. That, as well as his stature as the doyen of the microphone (Richie Benaud still cites him as his commentating inspiration, and the way he called home his own beloved horse Attivo in the 1974 Triumph Hurdle at Cheltenham remains the gold standard for commentary-box objectivity) is why his name has been appended to the National Hunt Chase at the Festival next Wednesday.

He first drove himself to Cheltenham – in the red Morris 8 coupé his indulgent grandparents, Sir John and Lady Henry, had given him for his 17th birthday – in 1935. Winning the fourth of five Gold Cups that year was the remarkable Golden Miller – "by three parts of a length from Thomond II," O'Sullevan recalls, as if it were yesterday – but Arkle, the winner in 1964, 1965 and 1966, is the horse he considers to have been the transcendent Cheltenham performer. To win the first of those Gold Cups, Arkle had to beat the formidable 1963 winner Mill House. Beforehand, the racing fraternity positively drooled with anticipation and I ask O'Sullevan whether the excitement surrounding next week's Gold Cup, and the confrontation between the stablemates Kauto Star and Denman, is comparable?

"Oh yes," he says, "although the situation is almost reversed. The big horse then was Mill House, who had won the previous year's Gold Cup, against the pretender. Here the big horse is the pretender, against the more greyhound-like winner of the previous year's Gold Cup in Kauto Star. So it's different in that sense, but it's wonderfully exciting, and I must say that it speaks such volumes for the Corinthian spirit in National Hunt racing that they are taking each other on. A couple of decades ago it couldn't happen that a Coolmore or a Godolphin would field several of their best horses in a top race and risk devaluing them. It illustrates the health of the sport."

Not least of O'Sullevan's many virtues is his refusal, rare enough among people even 30 years his junior, to champion the old days over modern times. Surely he can think of some aspect of racing that was better way back when? "Do you know, I really don't think so," he says. "They say it's in a state of crisis but I go through my cuttings – I'm a dreadful magpie – and I find that racing has been in crisis for the last 60 years!" He chuckles, and raises a glass of red, just poured by the French patron of Le Suquet, who has known "monsieur OSoolyvan" since he was a barman in Deauville in 1959. I get the standard O'Sullevan toast. "Happy days," he says.

I invite him to apply his unique perspective to the Cheltenham Festival. How has it changed since 1935? "Well, it has become a focal point of the season, whereas it used to just happen. Really, there was not a great deal of difference between the National Hunt meeting and any other. One catalyst was M V [Vincent] O'Brien, who was the first man to fly racehorses over the Irish Sea. In 1948 he flew three across, and most people thought they would be totally disorientated, yet Castledermot won the National Hunt Chase, to which they have so generously attached my name this year, Hatton's Grace won the Champion Hurdle, and Cottage Rake won the Gold Cup. Flying them had been considered sheer madness."

The charge of sheer madness could have been similarly levelled at anyone who, in O'Sullevan's boyhood, had predicted that he would push on into his nineties at a canter (almost literally, given the brisk pace at which he walks me from his flat to Le Suquet). "Yes, it's staggering I've got this far," he says. "I've had double pneumonia four times." Alcohol having blunted my manners, I ask whether he checks the obituary pages for news of his contemporaries? He indulges me with a chuckle. "I don't expect anybody to be around. So many of my generation went in the war, you know. It's a bizarre situation being so old, Brian. One is part-disenfranchised, as it were. My wife was 88 on 1 March, and our friends are very much younger than us. Except for two cousins of mine in Melbourne, there are no surviving relatives on either side."

In his teens he was so chronically asthmatic that doctors predicted he would not survive another English winter, and from Charterhouse he was dispatched to school in Switzerland. Later, he spent three months in Middlesex Hospital, suffering a facial skin condition so bad that he wore a medicated mask, Phantom of the Opera-style. But it did not stop him following his passion, and even expanding his contacts.

"I became very friendly while I was in the Middlesex with a man called Mackay, a racecourse tipster who wore an extravagant headdress and went by the name of Prince Monolulu. He was a great character; I have always referred to J H A McCririck as Monolulu without the feathers."

O'Sullevan issued his own tips from the pages of the Daily Express for 35 years, and was memorably persuasive in his endorsement of the 1956 Derby winner Lavandin. Indeed, he was never quite as persuasive again. "What really alarmed me was a letter from a nurse saying, 'I staked my future on your view of the 1956 Derby and I can't tell you what a difference it has made to my family'. It had gone well, but it could so easily have gone wrong. That was a very salutary lesson."

Nevertheless, it was not only the nurse who had cause to be cock-a-hoop that day. For O'Sullevan it was a particularly emotional win, because he had engineered a ride for his great friend Rae Johnstone "who by then was on Skid Row," and whose career was duly resuscitated. Almost as satisfyingly, it yielded a handsome sum from the bookmakers. "I said to my wife, 'Call Mario at the Caprice, darling, and tell him to reserve a table for 10'. She said 'Good God, you're crying.' I said, 'Of course I'm fucking crying..."

Our laughter turns even the heads of the lovebirds on the adjacent table. O'Sullevan is a masterly storyteller, quite happy to drop in the odd expletive when it adds piquancy to the tale, and like all the best storytellers he is a superb mimic; no one ever did a better Lester Piggott.

But what I have never heard him talk about in our various encounters down the years, I tell him, is sport beyond racing. Is he a fan? "Oh yes. I love other sports, and as a quick left-armer I used to play cricket quite reasonably, actually, given my health problems. And I think football now is utterly breathtaking, the chess that goes on, and how incredibly nimble they are. I don't really have a team, but I suppose I have a certain affinity for Chelsea." His eyes twinkle. "Having said that, I used to enjoy Stamford Bridge more when it was a dog track." Happy days.